Modern smart device-based concept of sensoric networks
© Behan and Krejcar; licensee Springer. 2013
Received: 9 October 2012
Accepted: 15 May 2013
Published: 6 June 2013
The modern society evolves into a sensorial network environment where individual sensor data can be transformed into cumulative and comprehensive representation for human. In a real time, it is independent of current location or behavior. The only limits to increase productivity and to create a smarter surrounding environment are personal habits and technology progress. The paper describes sensorial framework, which is dealing with the current aspects of technology, sociology, and usability in daily life usage of ubiquitous mobile devices with sensors, and arising computed and energy power. Nowadays, most of the common tasks of our lives are mainly influenced by network and social connectivity where infrastructural speed limits are provided by the information flow.
In the last few years, we have been witnessing the market explosion with the end-user mobile devices that are enhanced with many types of sensors. The time of plain non-sensorial smart phones is more or less over, and we are facing the future environment where built-in sensors as ambient temperature, magnetic field, accelerometer, gravity, light, humidity, and others are common equipment of current mobile devices [1, 2]. All of these sensors are supportive to the provided inner content. For instance, the user interface has been enhanced using gyroscope, and therefore, the visualization can be controlled by rotation or current position of a device . However, we might also start seeing sensors as receptors of global human body where, if we gather more sensorial data, we are being transformed into a smarter and more enhanced society. We recognized the most significant influence of sensors in computing estimation capability of surrounding environment and user behavior recognition where identification of human stereotypes is leading to the increase of productivity in terms of association corresponding processes with partial or full automation. Today’s low-cost sensorial technologies’ doors are opening up for daily life improvements and are shorting distances between content from producer and to consumer. Typically, the content could be served depending on current environment or user’s behavior. For instance, the user is located at a home environment, and therefore, the applications associated with the mobile device, such as home controlling or leisure, have higher priority. Under specific circumstances, we assume that the applications and content are so predictable that we could talk about Artificial User Interface as an improvement of device usability. Devices could offer predefined or the most preferred content launched automatically or initiate routines in specific circumstances.
Sensors within network-connected devices increase the capabilities of networks, and we assume that the internet is stepping into the sensorial network era where the key benefits are based in higher human productivity and openness of new sensorial informational channels. Those are personally related to behavior or environment, which leads to more open modern society. Although the openness could be noted as a negative factor due to the behavior, location, or environmental-based personal privacy information, that is, supposed not to be publishable, we consider that as a new opening stream of interpersonal communication which is from the view of historical context, more and more wanted to be open and available. That leads to the reduction of the privacy borders [4, 5]. The question is - are we prepared for a society based on free informational resources where any knowledge is reachable, and is it considerable to view it as a positive factor of human evolution?
The following sections describe the problem from a technical point of view of sensorial networks as well as the conceptual and architectural details of designed framework Senzoric.com. The benefit of sensorial framework research is aimed at effective distribution of information to corresponding interpersonal channels with consideration of current technological limits . Nowadays, the challenge is about providing important social relative information without explicit request definition.
2. Problem of sensory networks
All possible sensors of mobile devices are producing a large amount of data in total which are not necessarily to be transferred over network and reasonably shared in real time. That is why we could consider most of them in raw form as redundant or without meaningful informational value. Also, processing of sensorial values with maximal refresh data rate would be unreasonable in terms of battery management or use of non-real-time system bases.
2.1. Problem of sensors and their states
Type and unit
Motion sensor of three-dimensional X,Y,Z acceleration includes gravity magnitude which is g = 9.81 m/s2 and is expressed by following equitation:
Acceleration = − g − ∑ F/mass
To express pure acceleration, the gravity force must be removed from the data, and the result is basically a linear acceleration
From Android 1.5 API 3, from iPhone 3G 
Environmental sensor of one-dimensional ambient temperature in degree Celsius
From Android 4.0 API 14
Motion sensor of three-dimensional x, y, z vector indicating the direction and magnitude of gravity. The coordinate system is the same as acceleration
From Android 2.3 API 9
Motion sensor of three-dimensional x, y, z rotation vector around device’s local axis
From Android 2.3 API 9, From iPhone 4S
Environmental sensor of one-dimensional ambient light level indicator.
From Android 1.5 API 3, from iPhone 3G
Linear acceleration (m/s2)
Motion sensor of three-dimensional x, y, z linear acceleration vector indicating acceleration along each device axis, not including gravity. The coordinate system is the same within acceleration
Assume following equation:
Acceleration = gravity + linear − acceleration
From Android 2.3 API 9
Magnetic field (μT)
Motion sensor of three-dimensional ambient magnetic fields measured in micro-tesla in the x-, y-, z-axis.
From Android 1.5 API 3, from iPhone 3GS
Environmental sensor of one-dimensional ambient air pressure in hectopascal or millibar units
From Android 2.3 API 9
Environmental sensor of one-dimensional distance measured in front of the device
From Android 1.5 API 3, from iPhone 3G
Environmental sensor of one-dimensional relative ambient air humidity
From Android 4.0 API 14
Rotation vector (scalar)
Motion sensor of three-dimensional rotation vector expressed by following equation:
Value = sin(θ/2), where θ is the angle of device that has rotated around a specific axe
From Android 2.3 API 9, from iPhone 3G
Complementary sensors derived from smart devices
Type and unit
GPS (latitude, longitude)
Cell GSM (dB)
Location sensor type, where signal of access point results within external knowledge base in dynamic location monitoring.
Environmental sensor of noise level where a signal-to-noise ratio technique is appropriate for environment evaluation
Alternative way of a light sensor but with another applicability, as face or object recognition is out of energy scope
Battery capacity (%)
Sensor for smart reminding to charge in specific environment and smart battery management
Power plug-in (bool)
In building environment recognition
We divided the sensors into two groups where the first one is with short-term and second one is with long-term data change characteristics. According to the data amount, the first group required more frequent measurement to gather the correct sample of data for better pattern recognition, while the second group is resistant to infrequent precise measurement. Further in Table 2, we highlighted complementary sensors that are more related to pattern environment recognition than behavior.
From all available defined sensors, we announced which of them are contributory to specific behavior and environment pattern recognition with brief description.
Behavior patterns are the bases of motion effects of device sensors. That means recognition whether the device is worn and somehow influenced by a human body. The running motion is significant with fast location movements and periodical short shocks, while walking is distinguishable by lower shocks and slower location changes. By standing, we assume a static body position with small movement interferences, while sitting is more stable and longer lasting . Sleeping behavior is recognizable in deferred device position where surrounding specific pattern noise occurs. That was a brief description of basic motions, and more will be described in further discovery, as dancing, watching, gym, fun, etc. All of them are based on accelerometer, gyroscope, rotation, or magnetic field.
Another point of view is environmental-based resolution which is more limited and relies on external resource and social or network collected group knowledge. We defined the basic environment as home, work, transportation, or others which are less statistically probable. The home environment is recognizable as a place located overnight staying with the most count of occurrences in time. Work environment is a place located over recognizable specific equal time duration consumption over an awaken user state and most likely during a day in a different location than home. The transportation by car, plane, boat, train, bike, etc., is recognizable by the speed of a device, respectively, measured by location differences. Therefore, environment recognitions are essential location sensors and supportive sensors as humidity, temperature, pressure, light, and charging indicator.
2.2. Connectivity and data management
The connectivity is a basic factor which influences the necessity of transmitted data where the aggregation ratio between raw sensorial data and representational device state information implicates a reasonable data stream, which competes to be the most effective informational dataflow in time, energy consumption, and expected system functionality of delivery. We consider the minimal granularity of sensor’s transmitted information as bounded by maximal network throughput dependable on mobile device connectivity over well-known standards General Packet Radio Service, Enhance Data rates for GSM Evolution (EDGE), Universal Mobile Telecommunication System (UTMS), High Speed Packet Access, Wireless Local Area Network (WLAN), or Worldwide Interoperability for Microwave Access (WiMax). We also see considerable differences between Quality of Service according to a network type, current distance between mobile device and network access point, and other environmental circumstances.
Wireless network limits for mobile devices
Bandwidth (D/U Mbps)
Distance range (km)
10 to 35
100 to 1,200
3 to 10
2 to 5
5 to 30
50 to 500
20 to 50
10 to 40
5 to 30
5 to 30
0.001 to 0.5
10 to 100
400 to 1,000
300 to 900
5 to 10
0.001 to 0.005
The results (Table 3) were gathered from approximately 400 mobile devices by downloading applications from market. We expect to elaborate the statistics over time and cover all available network types in further discovery.
2.2.2. Information flow
Behavior and environment information
Behavior - walking
Behavior - running
Behavior - sleeping
Behavior - standing
Behavior - sitting
Behavior - driving
Environment - home
Environment - car
Environment - work
The minimal transition bundle of information has to consist of pattern identification (4B), timestamps (8B*2) of starting and ending time of recognition, location (8B*2) of latitude and longitude and the last device id or temporary token (16B). Therefore, a real-time data transmission has a minimal size (52B) in online mode delivery, which is not energy efficient. We also consider an offline mode for data flow, where the lists of recognition states are transferred over network that is demanded by remote request or periodically uploaded to data distribution server by time period or buffer size limit. The data flow type of service is according to battery management limited in real-time processing; therefore, the historical and current data are flushed to server only if required, with possibilities of in-time authorization on the producer’s side. Otherwise, in case of real-time processing requirements where the predefined authorization variant exists, the data flow depends on the point of interest and on the status change events with maximal battery effectiveness of sensor data gathering.
Other aspect, which would be taken in consideration, is network availability where the online mode is in fact commonly expected during the day, but it may also occur on specific occasions when the mobile device is temporarily or in the long-term without network connection. In that case, we expect to continue saving locally the desired sets of sensorial information for correct results in the objective of large scale. Therefore, the data could be stored on the device locally with optional network batch upload later on.
2.3. Battery management
According to the tested results from discovery , the energy consumption of localization sensors is the most effective in Global System for Mobile communication (GSM) cell bases evaluation where energy costs lowest than <20 mJ followed by WLAN around 545 mJ while Global Positioning System (GPS) sensor is consuming much more >1,424 mJ. Therefore, the priority in location estimation is about to be used as available capability as ordered by energy efficient factor. Other facts, which are suppressing energy sustainability, we consider to be redundant sensors where key efficient way is lower than information provided according to frequent measurements. Therefore, the principal use of the battery efficiency, we concluded, would be as linear acceleration in combination to cell location bases where uploading time in real-time behavior is about 1 s. Other sensors are beneficial only if battery is in the charging mode. In another words, the consumption nowadays is essential for usability of mobile devices where there is also required the implementation of such benefits as a battery recharge reminder, which in home environment reminds you to plug in your mobile device to power supply.
3. Related works
Activity recognition system  was developed as a real-time monitoring system for mobile devices that embrace neuronal network motion pattern recognition by body accessories, wirelessly connected over Bluetooth to provide sensorial data. The proposed solution requires additional components outside of the mobile device and additional energy consumption for local communication .
Another related work  considers providing sensorial information by context-aware web browsers which are able to merge web application tags with current mobile device sensorial data but only as a foreground process invoked by user actions, and therefore, for smart environmental-behaving solutions, it is insufficient.
On the other hand, InContexto  is a solid work that represents background service with still, walk, and run recognition with 97% accuracy, but the only sensor used for gathering this data is accelerometer which is not enough for larger scale of behavior and environment recognition.
For environment recognition and connected activities, where data is being minded in a recorded log, the case is to predict or analyze future patterns or to recognize the environment as a great work  where the point of view of soft sensors is taken into account, but the hard sensor are considered as a future possible improvement.
Related work functions summary
–/0.6 to 2/5
1 to 7/5/5
Sampling window size
1 to 15
2 to 10
1 to 7
Effective battery consumption
Pattern recognition type
According to the demonstrated summary in Table 5, it is hard to find a complex solution around all the mentioned solutions. This fact leads us to design and develop a new architecture as well as to implement some parts to provide a basic evaluation of the proposed solution. This will be outlined in the next few sections.
4. Proposal concept
The consumers are accessing the gathered data by web interface with aggregating functions by web console upon request, or the data are pushed down to subscribed device by cloud messaging, email, Short Message Service, and others. Overview of prototype side ‘Producer’ is described in more detail in the following section.
4.2. Middle ware
Development tools are open source based and preferred by Java programming language whenever it is possible. The development environment Eclipse provides beneficial features as a remote system-controlling Unified Markup Language diagram and model generation from Java code or additional program and code measurements and metrics evaluation. We describe the following parts from implementation point of view and describe key factors for success software prototype implementation.
5.2. Middle ware
The middle ware is implemented in Java and running on remote VPS on the Czech backbone network datacenter as Linux service used CentOS 6. Development corresponds with Rapid Application Development; therefore, Object Relation Mapping suites Java Persistent Api technology, which is provided by EclipseLink 2.3.2. as a data mapper and allows fast and comprehensive data management. The data objects are defined in Java classes, and relations between entities are expressed as members of a concrete class with specific annotation, specific cardinality and type of relation. The objects are transformed to the database through persistent commands, and after a commitment, they are saved to a hard file on a disk. Database engine is used in object database ObjectDB for its excellent performance which is running on the same server as the service. Tomcat is used as a web server with dynamic web module that allows Servlet 3.0 annotations directly into classes instead of configuration file web.xml. Consumer requests are served over HTTP request/response by JSON due to the simple and fast remote data access, which is used by a web client or Java console. For web service,  used a Representational State Transfer technology, which provides fast, comprehensive, and well-maintainable implementation, and allows multidata-type output assembled by simple annotation.
The prototype application that we developed consists of three components: producer, consumer, and middleware base on proposal concept. The minimal sampling rate for recognition activities and environment is gathered from measured data and corresponds with the table above (Table 4). Currently, we are gathering data from a crowd by free distribution application on the market and by testing user suitability and battery consumption. Furthermore, we enable connecting tasks based on activity and environment recognition. The solution overviewed (Table 5) is in parts as a motivation of improvements. On the other hand, from the usability point of view, the external sensors are out of scope for daily life routines and other systems are overheated by data without reasonable user conclusions or influence. The key to providing smart environment based on a mobile device application is in definition of goals and establishing an effective balance of used sensors data providers, where the minimization of power consumption is essential.
6.1. Privacy assumptions
The privacy is important issue for current social network services. Therefore, we assume that there are three security levels which fulfill the individual’s privacy requirements regarding the usage of Senzoric framework.
The first one can be seen from the network payload perspective where sensitive data could be captured by ‘man in the middle.’ We provide Secured Socket Layer communication between consumer and producer over all middleware. Therefore, only the knowledge of 4,096 bits of RSA key would be able to breakdown ciphered payload transmitted over the network.
The second perspective is from the database point of view. We consider most data provided from sensors and stored in database as anonymous data collections where no passwords or user details are stored. The whole process of association anonymous data collection to specific user is based on a token which is generated on user’s device by BCrypt  function from password or identity of third parties. Therefore, full database access rights are not eligible to associate user’s identity to concrete datasets. The only knowledge which could be data minded from database are statistical overviews and anonymous data interpretations.
The last perspective is done from application point of view where the access token is stored on each device in memory cache for correct association of device within the whole system. That could be captured on rooted android mobile devices, but we are not responsible for malicious software and user decisions.
6.2. Efficiency of assumptions
We use, as future discoveries are made, this ratio of informational extraction effectiveness and employing of neural networks for pattern recognition instead of simple intensity computation model.
The problem of behavior and environmental application development for mobile devices was presented. The effective concept for distributive sensorial information creates a challenge concerning the battery consumption, communication, and effective recognition aspect. All of these aspects are evaluated equally in order to help to increase the usability. We proposed application concept that is available for testing with real users from whom the data are gathered. The key benefit of the proposed architecture is in scalability and applicability for further location, motion, and environmentally based real-time solutions.
Future trends of sensorial networks and smart solutions based on them are founded in global knowledge of motion and environmental recognition. It is also built as automated assigned appropriate process that recreates a new society where one is driven by smart solutions and decision makers . For instance, one will never wait in a situation where traffic periodical mechanism is provided without global sensorial network knowledge, which can have an impact on various kinds of day life activities [1, 30, 31].
The work proposes effective information distribution within minimal usability impacts on device, user, and networks. In the future, the social networks and sensor networks will merge. We stand at the beginning of a new era of sensorial social networks where we will perceive only information which is relevant to us. In other words, we will create, through our activities, our own artificial informational shield or receiver, and through our life style, we will obtain corresponding informational channels.
The work and the contribution were partially supported by the project (1) ‘Smart Solutions in Ubiquitous Computing Network Environments,’ Grant Agency of Excellence, University of Hradec Kralove, Faculty of Informatics and Management; (2) ‘SmartHomePoint Solutions for Ubiquitous Computing Environments,’ University of Hradec Kralove under the project number SP/2013/3. We also acknowledge supported from Cautum Company (http://cautum.cz/). Last, but not the least, we acknowledge the technical language assistance provided by Jirina Cancikova (Universidad de Burgos, Spain) and Stanislava Horakova (University of Warwick, UK).
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